Cable system operators use Radio Frequency (RF) signals transmitted over coaxial cables to provide television and data services to customers. Normally these RF signals do not cause interference when in compliance with Federal Communication Commission (FCC) rules that limit interference. However, in some cases the RF signals can leak. Cable signal leaks occur when the RF signals transmitted within the cable system are not contained within the cable plant. Cable signal leaks may be caused by loose connectors, damaged cables, unshielded housings, or unterminated cables.
A cable plant uses many of the same frequencies to transmit programming as licensed to over-the-air broadcasters. Cable operators are considered by the FCC to be secondary users of these frequencies, so they are precluded from interfering with licensed users who are the primary users of these frequencies.
Cable signal leakage can interfere with the over-the-air services that are using the same frequencies as the cable plant near the vicinity of an RF leak. This can interfere with ham radio operators, cellular radio, emergency responders, and aircraft navigation systems. When interference from the cable plant occurs, it can hamper or endanger others.
The FCC has set maximum individual signal leakage levels for cable systems. The FCC is stricter with signal leakage levels for cable systems that interfere with aeronautical and/or navigation communications. Therefore, the FCC requires cable operators to have a periodic, on-going program to inspect, locate, and repair RF leaks in their cable plants. However, locating RF leaks in a cable plant can be difficult and time consuming, due to the complexity and size of a typical cable plant.